Metabolism and Energy Balance – everything you need to know about fat burning

Author: Nikolay Kaufman 16.09.2022

Table of content
1. What do you need to know about gaining and losing weight?

1.1 What is energy balance and the CICO model? 

2. Why are we all so different in terms of our metabolism? 

2.1. Basal Metabolic Rate – Resting Basal Metabolic Rate
2.1.1. Exactly how much does our metabolism slow down? 

2.2. Thermic Effect of Food 

2.3. Exercise Activity Thermogenesis 

2.4. Non – exercise activity thermogenesis
2.4.1. Some people can speed up their metabolism twice as much!

3. Are there people with fast and slow metabolisms? 

4. How can we speed up our metabolism?
4.1. Meal frequency? 

4.2. Size of meal?
4.3. Higher protein intake?
4.4. Better sleep?
4.5 Deliberate movement?

4.6 Nutritional supplements? 

5. What you need to know about the energy balance and metabolism 

The topic of metabolism is one of the most discussed in the world of fitness. We are all interested in exactly how to lose weight, why we sometimes reach a plateau or stagnation and why some people have a “fast” and others a “slow” metabolism. Is it related to physical activity? Or is it to do with diet quality? Those, who never gain weight and stay lean, and have difficulty when they need to increase their personal weight, we categorise as hardgainers. And those who gain weight easily are advised to eat 8 times a day to speed up their metabolism. There are many myths and legends about metabolism and fat burning. The truth is that metabolism is surprisingly stable and can be calculated with great accuracy in the laboratory.

In fact, the true meaning of the word metabolism is “change.” Metabolism is a set of life – supporting chemical reactions, processes and functions taking place in the human body. For example, we can talk about carbohydrate metabolism – the process of carbohydrate absorption in the body. We can also talk about metabolic pathways – a specific cascade of reactions taking place in the body. Imagine them as a machine with dozens of cogged wheels that engage one with another. When it comes to losing or gaining weight and body fat, the thing that matters is something completely different, called Energy Balance. Note that when someone talks about metabolism, they may mean one of two things:

Resting basal metabolism (RBM) – the amount of energy the body needs to maintain vital functions in a state of complete rest.

Energy balance – the complex relationship between the consumed calories and the expended calories, which in the long run determine whether we burn or gain fat.

What do you need to know about gaining and losing weight?

If we don’t have a good understanding of the conditions under which we gain or lose weight, our diet will never be successful! It’s all determined by energy balance – the relationship between the calories we take in and the calories we expend. It refers to the laws of thermodynamics and those that relate to energy transfer and energy storage. Energy balance is directly related to the first law of thermodynamics, which states that there is no energy lost. Applying this to the human body, we conclude that when we take in more energy than we expend, it cannot be lost, and it should be stored. Energy is stored mainly in fat stores, which we all want to get rid of. Let me repeat – the energy we take in but do not expend is stored as fat. The same is true when we take in less calories than we expend – the energy must come from somewhere. Preferably it’s the fat depots, but if you don’t have a good diet, rich in high quality protein, carbohydrates, fats, minerals, and vitamins you will burn muscle first. Unpleasant, but a fact.

What is energy balance and the CICO model?

The relationship between the calories we take in and the calories we expend is often described by “CICO” – calories in versus calories out. Calories in is a relatively easy concept to explain. In 99% of cases, it’s about the calories we take in through food and the calories we manage to absorb. Calories out (calorie expenditure) is the trickier part of the equation, and this is where the big problems and confusion come in.

The reason is that while the CI (calories in) part can be controlled to a large extent and can even be fixed, the CO (calories out) part of the equation is extremely variable. Here are a few factors that can affect our energy expenditure:

Energy for sport activity and movement.

Heat produced through physical activity.

Heat produced by digesting and processing food.

Efficiency of food metabolism.

Energy expended to build and repair muscle tissue.

That’s not even the full list! For this reason, there are many people who say that calorie tracking doesn’t work for them, but that’s a topic for another article. Let’s take a closer look at what are the factors that determine our energy expenditure. Let me explain why this is necessary…

Why are we all so different in terms of metabolism?

For this purpose, it is necessary to get familiar with the 4 components of the human energy balance:

Resting Basal Metabolic Rate (BMR).

Thermic Effect of Food (TEF).

Energy expended for sports activity (Exercise Activity Thermogenesis – EAT).

Energy expended for spontaneous everyday movement (Non-Exercise Activity Thermogenesis – NEAT).

In this article, I will often use the acronyms used in academic articles for the information of those of you who are more curious and want to learn more about the topic!

Basal Metabolic Rate – Resting Basal Metabolic Rate

BMR represents the energy we expend at total rest. This includes the maintenance of the body temperature and other important processes that are necessary for the proper functioning of the human body. BMR is not as variable as many people believe. The confusion comes from the fact that it is often used synonymously with overall energy intake or energy expenditure. Of course, this is a very elementary and wrong reading. So, before we continue, it is very important to understand exactly how basal metabolic rate is measured. Usually, this is done in the morning on an empty stomach in total rest (lying down) and in a strictly controlled environment to exclude any kind of physiological and psychological stimulus. Conditions that in no way correspond to our daily life. Furthermore, BMR is only one component of the human energy balance. Nevertheless, it is the most constant and predictable variable of our energy expenditure. Resting basal metabolism is responsible for about 60% of energy expenditure. The factor that is most determinant of BMR value is muscle mass – it accounts for about ¾ of the variation in BMR value between people.

This means that if we compare two individuals – one with a “fast” and one with a “slow” (basal) metabolism, but with the same height and weight, we can explain at least 75% of the difference between their individual resting energy expenditure with the amount of muscle mass they possess. In that case, it’s not hard to explain why bodybuilders expend on average 14% more calories at rest than people of the same height and body fat! In a recent interview, Menno Henselmans mentioned the recent research he has carried out with the help of his team. Menno was sure that given enough control over all other factors, “the amount of muscle mass is the only determining factor of our BMR”! I have no doubts about Menno’s professionalism and results, but it is important to note that these studies have not yet been published in an academic journal. This would only confirm our recommendations that the amount of muscle mass is one of the most important factors in the success of a diet. As for the slowing of our metabolism because of prolonged dieting – it is very predictable, as it is primarily due to the loss of muscle mass. Therefore I have repeatedly stressed how important it is to preserve our muscle mass while dieting. However, there really is a slowing of the “metabolism”. For one, this is related to many changes in the hormonal environment. On the other, the body itself becomes more efficient in the process of absorbing and using energy, at a molecular level. This is mainly due to improved mitochondrial efficiency and changes in the hormonal environment, which stimulate decreased energy expenditure and increased hunger. Still, let’s put things in perspective.

Exactly how much does our metabolism slow down?

In this study, the researchers looked at: the difference in BMR at a loss of 10% of self-reported weight in normal-weight people; and 20% in overweight people. The group of 11 people with normal personal weight took 800 calories a day until they lost 10% of their weight. Their BMR decreased from 1511 ± 304 to 1290 ± 228 calories, and their weight from 70.5 ± 11.7 to 63.7 ± 10.1 kg. That is, about 220 calories on average on an aggressive diet that is not optimized to preserve muscle mass. Another interesting and more recent example is a study by Tremblay and Chaput (2009). The researchers looked at several factors, including BMR, in a group of 8 overweight men during a sustained 700 calorie deficit until reaching total plateau. This took 246 days, during which time the participants lost an average of 12.7kg and their BMR slowed by 168 calories. Ultimately, we are talking about overweight people who do not exercise. If we exclude the muscle mass lost, the additional BMR slowdown found in various studies ranges from 79 calories to 504 calories. Of course, these are extreme cases. The lesson is that we need to keep muscle loss to an absolute minimum so that we don’t have to reduce our caloric intake further because of BMR slowing down. For this we need to have a good diet and strength progress in our workouts!

Thermic Effect of Food – TEF

TEF is the energy that is required by the human body to break down, digest and store ingested food. TEF is a very variable component, because each of the three macronutrients has a different thermal factor:

Protein: between 20-35%.

Carbohydrate: between 5-15%, with some foods with more fiber this can be as high as 20%.

Fat: around 2-3%, with higher values for some types of fat. Medium chain fats have a thermic effect of about 15%.

Have in consideration! We also don’t eat macronutrients, we eat foods. In fact. we don’t eat foods in isolation either, we eat whole meals.

It also gets more complicated as TEF is very dependent on the percentage of body fat and the amount of muscle mass! In people with a high percentage of body fat, TEF goes towards the lower limit of 10%, due to impaired glucose intake and insulin resistance. In contrast, TEF can rise as high as 25% in people with perfect diets and low levels of body fatWhat you need to know about TEF is that it affects every one of the other components! It’s very simple – we get all our calories from food, which itself requires energy to digest. Let’s say I need 2000 calories a day to maintain my body temperature, for all the movement I do during the day, and for gym after work. It’s not enough for me to only consume 2000 calories from food, as it would take 10-25% of the value of the food itself to digest. Between 200 and 450 calories of the original 2000 would be burned, just to absorb and store the nutrients. In that case, I need to take between 2200 and 2450 to keep the equation constant and maintain my personal weight. This is one of the reasons people talk about slow metabolism on a longer diet. As you found out, the body’s own energy needs don’t slowdown that much, but as I need to take in less calories, the thermic index also decreases proportionally. If we continue the previous example and assume that as a result of the long-term diet my needs have been reduced to 1700 calories per day, then TEF equates to 170-425 calories.

Exercise Activity Thermogenesis

EAT is probably the easiest component to calculate – it’s the energy we expend during sport. For us, EAT equates to the energy we expend during weight training or cardio. There are many ways to calculate it, most represented as calories expended per kilogram of body weight per minute of a given activity. For most people, EAT tends towards 0 as they lead a sedentary lifestyle. Without overcomplicating the subject, we can assume that standard weight training requires between 300 and 450 calories.

Usually, weight training consumes 0.1 calories per minute for every kilogram of body weight (Bayesian Bodybuilding PT Course, Menno Henselmans; Advanced Nutrition and Human Metabolism, 5th edition). So, if you train for 70 minutes and weigh 70 kg, your workout amounts of calories is around 490 kcal. Furthermore, EAT also doesn’t change significantly much during diet or surplus. Here The main factor that matters our is work capacity. With a prolonged caloric deficit, it is inevitable that the amount of work we can do will be suppressed. The same applies to post-training recovery. However, with a good diet and training regime, this happens really in the final weeks before reaching a very low percentage of body fat. The change in EAT is so minimal that it’s not worth paying much attention to!

Non – exercise activity thermogenesis

NEAT includes absolutely every other movement you can think of. Walking in the park, climbing stairs, sitting, ironing clothes, washing dishes, even tapping your fingers on the table (fidgeting movements). And of course, that makes NEAT the most variable part of the human energy balance. NEAT is the most interesting, and if you have a good understanding of exactly what it means and how it works, you’ll be able to answer a lot of questions you’ve probably asked yourself at one point or another. Interestingly, even in professional athletes, NEAT accounts for a significantly larger portion of calories expended compared to EAT. Even in people with sedentary lifestyles, NEAT is about 15% of energy expended. In contrast, it can be as high as 50% of the expended energy in extremely active individuals. In fact, this is the thing that determines whether someone has a “fast” or a “slow” metabolism! The reason is that we all differ in our ability to adapt to a calorie surplus or deficit.

Some people can speed up their metabolism twice as much!

I can best explain all this by introducing you to a high – quality study. The researchers’ goal was to measure the extent of compensated calories for a calorie surplus of 1,000 calories through subconscious movement (NEAT). To do this, they took 16 healthy, young men and women who did not exercise and put them in a 1000 calorie surplus for 8 weeks. It turns out that one of the men was able to compensate for up to 70% (692 calories) of the excess! For him, the extra energy automatically led to a rise in body temperature and much more spontaneous movement. The result is that the actual surplus he was in was only 300 calories. On average, the study participants compensated for about 33% of the extra energy, or 328 calories. As a result, they found themselves in twice the caloric surplus. You can judge for yourself in which group a faster personal weight gain was seen.

Are there people with fast and slow metabolisms?

The short answer to this question is yes. The more serious answer is “but not exactly…”. We are all used to live in a certain routine. We organize our lives around our work, school activities, family obligations, and other tasks. In this way we maintain balance and in fact our calorie intake and expenditure are very similar from week to week. On a strict schedule, the energy we expend on sports is constant. However, we all exercise on certain days. Occasionally we may miss a workout or add an extra workout day into a particular week. However, the average person moves in a certain range, for example between 2-3, 4-5 training days per week. Unless there is a drastic weight loss, BMR is also a completely constant variable. Although in some cases our diet may be drastically different from day to day, the thermal index of food does not vary enough to affect our weight. Why, then, there are people who don’t gain weight and stay lean and those who gain weight only when they look at a piece of cake?

We have reached the last component of the human energy balance – NEAT! Remember the study I quoted above? There are able to compensate up to 70% of their caloric intake through increased spontaneous physical activity. This is a natural progression in human evolution, as these people adapt extremely quickly under extreme conditions, such as overeating or starvation. For this reason, it is more correct to divide humans into those with “adaptive” and “maladaptive” metabolisms. Interestingly, the adaptability of any organism applies to both calorie surplus and calorie deficit. So, these same people who are gaining weight super hard have to do a very aggressive diet to get to a competitive bodybuilding level.

How can we speed up our metabolism?

As for resting basal metabolism, the answer is very simple – build more muscle mass. I guess this is already a goal of our readers, so I’m hardly telling you anything new. Besides, you’re all already training with weights and there’s no way to increase your energy expenditure during a workout, except to extend the workouts themselves or add cardio. Instead, we can influence the thermic index of food by improving our diet or unconscious movement during the day, or by sleeping better.

Meal frequency?

You must have probably heard the traditional advice to eat often? This may be appropriate for some herd animal that has survived and has more than one stomach, but the human body is not set up that way. The frequency and size of different meals have no effect on metabolism. In terms of thermic effect, it doesn’t matter if we spread the meals out into 8 x 300 calorie meals or 4 x 600 calorie meals. The energy we need to digest food is the same.

Size of meals?

Another common tip is to eat a big breakfast. After all, this is the most important meal of the day, right? Not really. It’s true that spontaneous movement and therefore our energy expenditure increases after a more substantial breakfast. But this effect doesn’t just apply to the first meal of the day! In fact, it’s true for every meal. Once we take in a meal, our energy expenditure increases in proportion to the caloric value of the meal itself. Larger portions have been reported to have a higher heat index than the same meal divided into several smaller portions, but the difference is minimal.

Higher protein intake?

Protein is the macronutrient with the highest thermal index. For this reason, many nutritionists and gurus recommend an increased protein intake. Although it has many beneficial qualities, it doesn’t sound realistic to stuff ourselves with protein just because of its thermal index. Especially considering what the reason for the elevated heat index is, that protein is much harder to break down. It’s true that a high-protein diet won’t harm you unless you have inherited kidney disease, but it can still cause discomfort due to absorption difficulties.

From another point of view, too high an intake, of any macronutrient, can lead to an imbalance of our whole diet! Even in the most optimistic scenario, where you would replace 45g of fat for 100g of protein, you would consume about 70 calories more. This statement applies more to those of you who don’t get enough protein.

Better sleep?

The link between low-quality sleep and obesity is well described in the science literature. Just one night of sleep deprivation leads to elevated ghrelin (hormone responsible for hunger hormone) and cortisol (the stress hormone) levels. This in turn increases caloric intake and lowers energy expenditure. The reason is that sleep is a natural energy storage mechanism. When we sleep, we need significantly less energy. This may seem strange to us, but it has been extremely important to the survival of our entire species. It seems logical that we would experience greater hunger if we were sleep deprived, as we have most likely expended more energy to stay awake! At the same time, our body reduces spontaneous and subconscious movement during the day to conserve extra energy. Chronic sleep deprivation has a strong negative effect on macronutrient absorption, insulin sensitivity and it lowers the anabolic potential of our workouts! Sleep quality has so many positives that I don’t know where to start without writing an entire article. What you need to remember is that sleep is the most effective way to ” speed up” your metabolism.

Deliberate movement?

Very popular advice is to move more. From a theoretical point of view this is great advice – more movement = more expended calories. But in practice, things are quite different. Consciously forcing ourselves to do something we don’t enjoy takes a lot of willpower and energy. Usually this translates into a huge amount of cardio, but not only. A typical tip is to take the stairs instead of using an elevator or escalator. Or to walk instead of using public transport. This will increase your energy expenditure, but if such behavior doesn’t come from within, it leads to unnecessary stress. What happens when the stress builds up and the willpower isn’t there? Total failure or not following the established regimen. Sometimes this is enough to erase 2-3 weeks of your progress. What is the solution? Find what you enjoy – running, soccer, swimming, basketball, cycling, etc.

Nutritional Supplements?

Of course, there are many products that are supposed to speed up the metabolism. Well, the truth is quite disappointing. The only working ingredient in most pre-workout products and fat burners is caffeine.

Naturally, its effect also comes with certain conditions:

You shouldn’t have a built-up tolerance to it.

It takes several hundred milligrams of caffeine to have any effect.

Even then, your metabolism will spike by between 3 and 11 %, and that’s just for a few hours. If you overdo with caffeine or other stimulants, it’s quite possible that your sleep quality will suffer.

What you need to know about the energy balance and metabolism?

The success of any diet depends on our individual energy balance – the dynamics between the calories we take in and the calories we expend. We call this pattern CICO (calories in vs calories out). The human energy balance consists of 4 separate components. Each one contributes to our energy expenditure. Resting basal metabolism is just one of them and contrary the popular claims, it is relatively stable. In fact, the main difference between all of us comes from: the amount of muscle mass we have; the thermic factor of the food we ingest; and the unconscious movement during the day. It is the spontaneous physical activity the component that distinguishes people with a “fast” metabolism from those with a “slow” one. Some of us can compensate for an enormous amount of excess energy by constant movement during the day. Others must find their own way to speed up their metabolism to have a successful diet. The most effective way is to pay attention to your sleep. The quality of your diet and the amount of muscle mass you have can also have a significant impact. As for physical activity – consistency is the most important factor. Therefore, people who try to force themselves to do a certain type of activity don’t do well in the long term. There are no magical supplements that will help you instantly, nor are there diet methods or special foods that cause instant fat burning. If you want to get rid of fat you need to make sure you are in a calorie deficit for enough time, pay attention to your sleep and diet, and maintain as much muscle mass as possible!

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